Vibration question for you Pros

[dpelletier]

I just installed a new 720BE on my Synergy E5 and thought I would take a look at vibrations.
There is an occasional "fore and aft" peak around 20,000 rpm. Peaks in high 20s.
Must be the motor but I'm not sure as to why it only pops up here and there if something was out of balance it would be more consistent right?
Here is the gearing info.
Helicopter is 550 size with 556mm main blades
Running 6S, motor is a 1100KV
Governed head speed around 2300rpm
Main gear 119, pinion 14
Outside temp was approx 40F or 5C
I've attached the log file, any insights or thoughts would be welcome.

[Xrayted]

Originally Posted by dpelletier

I just installed a new 720BE on my Synergy E5 and thought I would take a look at vibrations.
There is an occasional "fore and aft" peak around 20,000 rpm. Peaks in high 20s.
Must be the motor but I'm not sure as to why it only pops up here and there if something was out of balance it would be more consistent right?
Here is the gearing info.
Helicopter is 550 size with 556mm main blades
Running 6S, motor is a 1100KV
Governed head speed around 2300rpm
Main gear 119, pinion 14
Outside temp was approx 40F or 5C
I've attached the log file, any insights or thoughts would be welcome.

Yes that's the motor, but its likely spiking like that when you do something suddenly loads the motor up, which is not uncommon. My motor will also throw spikes like that on hard moves or poor collective management. Its not a constant vibe like we would see with an out of balance situation. If you had your unit set to record playback files, we could map your stick movements to the vibe file and see exactly what stick movement correlates to the spikes. Unfortunately vibe files only contain the basic vibe info.

There are bigger issues though, as your baseline vibes are too high all the way across and very noisy, staying near 6 pretty much all of the time at their lowest. The vibe files looks like your unit is too rigidly mounted to me. Are you using the metal plate and the thick and thin foam mounting method?

If so, then you are mounted in a bad spot on the heli or either the gyro is touching the heli frame somehow, or more likely the wiring going into the unit is bound up too close to the unit and transferring vibes into the unit.

A picture of your setup would be helpful.

[dpelletier]

Hey XR, thanks for the input.
I would put my money on poor collective management for the motor vibes.

I am indeed using the thick tape under the steel plate and thin for the 720.
The unit is mounted in the provided space on the helicopter. Its probably the wires.
I'll loosen up the bundle and change the logging to flight and try again tomorrow.
Here are two photographs.

Thanks

[Xrayted]

Originally Posted by dpelletier

Hey XR, thanks for the input.
I would put my money on poor collective management for the motor vibes.

I am indeed using the thick tape under the steel plate and thin for the 720.
The unit is mounted in the provided space on the helicopter. Its probably the wires.
I'll loosen up the bundle and change the logging to flight and try again tomorrow.
Here are two photographs.

Thanks

The wires don't look too bad actually, but in my experience mounting directly over the tail box is very high in vibes. Unfortunately that is where they put the gyro mount on many helis. You need a few CM of loose wires before they enter the unit without binding them together, and you look to be fine.

I had the same issue with my Align 500 Pro, and got much better results mounting the unit down between the frames on the lower skid mount plate, although it was tight in there, and not so easy to reach the USB plug. Its no problem if you can keep the vibes below the SL cutoff threshold. What are your total vibes in flight? Plug the unit into the SL software and choose the Voltage, RPM and vibe score under the View drop-down
This must be below 7 in order to keep your SL from shutting off in flight.

Another option that works well would be to use the same location, but a softer and better vibe absorbing materiel like Zeal gel instead of the more rigid foam pads. Zeal will cut your vibes reaching the unit a good bit, and is one of my favorites for the way I fly. Its not for everyone though, and not always liked so well by hard 3D smack guys who prefer a very rigid mount. You will never notice if you are sport flyer. http://www.amazon.com/dp/B002U2GS2K/...l_1s4sy23hxi_b

Another easy trick to try is to trim the two foam pads you are using now so you have four smaller square pads in the corners vs. two long pads. Less contact surface = less vibes making it into the unit, but once again you may end up with a mount that is just as soft as the Zeal gel, so it takes some trial and error to get it worked out the best for your needs. My Goblin works great with one solid block of Zeal the same size as the metal plate, and I've tried all sort of combinations of other materials.

[nanmadpad]

Do you use the zeal tape with the aluminum plate and the thin tape that is between the fbl and plate. In other words the zeal tape replaces the thick foam tape. Do you cut the zeal tape to fit the entire size of the plate.

[Xrayted]

Originally Posted by nanmadpad

Do you use the zeal tape with the aluminum plate and the thin tape that is between the fbl and plate. In other words the zeal tape replaces the thick foam tape. Do you cut the zeal tape to fit the entire size of the plate.

In my case, I use a solid block of Zeal the size of the the plate along with the plate as you describe.

You can get the vibes a little lower splitting the Zeal into two strips like the foam, however the Zeal is already a softer mounting material, and I think its too soft when split, especially in the hot Summer months.

[nanmadpad]

Which pad do you use between the plate and the fbl when using the zeal

[Xrayted]

Originally Posted by nanmadpad

Which pad do you use between the plate and the fbl when using the zeal

I just use the grey 3M/Scotch double sided tape with the red backing found at Home Depot, etc for mounting my gyros to the plate. Super strong stuff, and can be peeled off easily when needed without tearing into tiny little pieces like the supplied thin, white tape from SK.

http://www.homedepot.com/p/Scotch-1-...vZc5dkZ1z0t5gn This is the "extreme" 20lb support version, but they have a standard 10lb version as well. Either works fine

[nanmadpad]

Thank you

[highjinx]

Not to jump in on you guys..... but I've found out this winter that after a summer of changing everything on my heli (Align 550e with SK-720 black) including a new KDS motor that I finally had gotten rid of all my vibs...and that was with changing my gyro mounting tape back to the Skookum black foam...... But as soon as the temp here got below 0 c or 32 f that the Skookum Robotics black foam (that over the summer ended up fixing all my vib issues) is now much stiffer and once again my vibs are back. Your heli could be fine, but not when its outside in cold weather.

[dpelletier]

That's a good point.

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